/* * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "code/codeCache.hpp" #include "code/compiledIC.hpp" #include "code/icBuffer.hpp" #include "code/nmethod.hpp" #include "compiler/compileBroker.hpp" #include "memory/resourceArea.hpp" #include "oops/method.hpp" #include "runtime/atomic.inline.hpp" #include "runtime/compilationPolicy.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/orderAccess.inline.hpp" #include "runtime/os.hpp" #include "runtime/sweeper.hpp" #include "runtime/thread.inline.hpp" #include "runtime/vm_operations.hpp" #include "trace/tracing.hpp" #include "utilities/events.hpp" #include "utilities/ticks.inline.hpp" #include "utilities/xmlstream.hpp" #ifdef ASSERT #define SWEEP(nm) record_sweep(nm, __LINE__) // Sweeper logging code class SweeperRecord { public: int traversal; int compile_id; long traversal_mark; int state; const char* kind; address vep; address uep; int line; void print() { tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " PTR_FORMAT " state = %d traversal_mark %ld line = %d", traversal, compile_id, kind == NULL ? "" : kind, p2i(uep), p2i(vep), state, traversal_mark, line); } }; static int _sweep_index = 0; static SweeperRecord* _records = NULL; void NMethodSweeper::report_events(int id, address entry) { if (_records != NULL) { for (int i = _sweep_index; i < SweeperLogEntries; i++) { if (_records[i].uep == entry || _records[i].vep == entry || _records[i].compile_id == id) { _records[i].print(); } } for (int i = 0; i < _sweep_index; i++) { if (_records[i].uep == entry || _records[i].vep == entry || _records[i].compile_id == id) { _records[i].print(); } } } } void NMethodSweeper::report_events() { if (_records != NULL) { for (int i = _sweep_index; i < SweeperLogEntries; i++) { // skip empty records if (_records[i].vep == NULL) continue; _records[i].print(); } for (int i = 0; i < _sweep_index; i++) { // skip empty records if (_records[i].vep == NULL) continue; _records[i].print(); } } } void NMethodSweeper::record_sweep(nmethod* nm, int line) { if (_records != NULL) { _records[_sweep_index].traversal = _traversals; _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark; _records[_sweep_index].compile_id = nm->compile_id(); _records[_sweep_index].kind = nm->compile_kind(); _records[_sweep_index].state = nm->_state; _records[_sweep_index].vep = nm->verified_entry_point(); _records[_sweep_index].uep = nm->entry_point(); _records[_sweep_index].line = line; _sweep_index = (_sweep_index + 1) % SweeperLogEntries; } } void NMethodSweeper::init_sweeper_log() { if (LogSweeper && _records == NULL) { // Create the ring buffer for the logging code _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); } } #else #define SWEEP(nm) #endif NMethodIterator NMethodSweeper::_current; // Current nmethod long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: // 1) alive -> not_entrant // 2) not_entrant -> zombie // 3) zombie -> marked_for_reclamation int NMethodSweeper::_hotness_counter_reset_val = 0; long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes); class MarkActivationClosure: public CodeBlobClosure { public: virtual void do_code_blob(CodeBlob* cb) { assert(cb->is_nmethod(), "CodeBlob should be nmethod"); nmethod* nm = (nmethod*)cb; nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); // If we see an activation belonging to a non_entrant nmethod, we mark it. if (nm->is_not_entrant()) { nm->mark_as_seen_on_stack(); } } }; static MarkActivationClosure mark_activation_closure; class SetHotnessClosure: public CodeBlobClosure { public: virtual void do_code_blob(CodeBlob* cb) { assert(cb->is_nmethod(), "CodeBlob should be nmethod"); nmethod* nm = (nmethod*)cb; nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); } }; static SetHotnessClosure set_hotness_closure; int NMethodSweeper::hotness_counter_reset_val() { if (_hotness_counter_reset_val == 0) { _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; } return _hotness_counter_reset_val; } bool NMethodSweeper::wait_for_stack_scanning() { return _current.end(); } /** * Scans the stacks of all Java threads and marks activations of not-entrant methods. * No need to synchronize access, since 'mark_active_nmethods' is always executed at a * safepoint. */ void NMethodSweeper::mark_active_nmethods() { assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); // If we do not want to reclaim not-entrant or zombie methods there is no need // to scan stacks if (!MethodFlushing) { return; } // Increase time so that we can estimate when to invoke the sweeper again. _time_counter++; // Check for restart assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid"); if (wait_for_stack_scanning()) { _seen = 0; _current = NMethodIterator(); // Initialize to first nmethod _current.next(); _traversals += 1; _total_time_this_sweep = Tickspan(); if (PrintMethodFlushing) { tty->print_cr("### Sweep: stack traversal %ld", _traversals); } Threads::nmethods_do(&mark_activation_closure); } else { // Only set hotness counter Threads::nmethods_do(&set_hotness_closure); } OrderAccess::storestore(); } /** * This function triggers a VM operation that does stack scanning of active * methods. Stack scanning is mandatory for the sweeper to make progress. */ void NMethodSweeper::do_stack_scanning() { assert(!CodeCache_lock->owned_by_self(), "just checking"); if (wait_for_stack_scanning()) { VM_MarkActiveNMethods op; VMThread::execute(&op); _should_sweep = true; } } void NMethodSweeper::sweeper_loop() { bool timeout; while (true) { { ThreadBlockInVM tbivm(JavaThread::current()); MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); const long wait_time = 60*60*24 * 1000; timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time); } if (!timeout) { possibly_sweep(); } } } /** * Wakes up the sweeper thread to possibly sweep. */ void NMethodSweeper::notify(int code_blob_type) { // Makes sure that we do not invoke the sweeper too often during startup. double start_threshold = 100.0 / (double)StartAggressiveSweepingAt; double aggressive_sweep_threshold = MIN2(start_threshold, 1.1); if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) { assert_locked_or_safepoint(CodeCache_lock); CodeCache_lock->notify(); } } /** * Wakes up the sweeper thread and forces a sweep. Blocks until it finished. */ void NMethodSweeper::force_sweep() { ThreadBlockInVM tbivm(JavaThread::current()); MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); // Request forced sweep _force_sweep = true; while (_force_sweep) { // Notify sweeper that we want to force a sweep and wait for completion. // In case a sweep currently takes place we timeout and try again because // we want to enforce a full sweep. CodeCache_lock->notify(); CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000); } } /** * Handle a safepoint request */ void NMethodSweeper::handle_safepoint_request() { if (SafepointSynchronize::is_synchronizing()) { if (PrintMethodFlushing && Verbose) { tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count()); } MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); JavaThread* thread = JavaThread::current(); ThreadBlockInVM tbivm(thread); thread->java_suspend_self(); } } /** * This function invokes the sweeper if at least one of the three conditions is met: * (1) The code cache is getting full * (2) There are sufficient state changes in/since the last sweep. * (3) We have not been sweeping for 'some time' */ void NMethodSweeper::possibly_sweep() { assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); // If there was no state change while nmethod sweeping, 'should_sweep' will be false. // This is one of the two places where should_sweep can be set to true. The general // idea is as follows: If there is enough free space in the code cache, there is no // need to invoke the sweeper. The following formula (which determines whether to invoke // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, // the formula considers how much space in the code cache is currently used. Here are // some examples that will (hopefully) help in understanding. // // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since // the result of the division is 0. This // keeps the used code cache size small // (important for embedded Java) // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula // computes: (256 / 16) - 1 = 15 // As a result, we invoke the sweeper after // 15 invocations of 'mark_active_nmethods. // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula // computes: (256 / 16) - 10 = 6. if (!_should_sweep) { const int time_since_last_sweep = _time_counter - _last_sweep; // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time, // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive // value) that disables the intended periodic sweeps. const int max_wait_time = ReservedCodeCacheSize / (16 * M); double wait_until_next_sweep = max_wait_time - time_since_last_sweep - MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled), CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled)); assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect"); if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { _should_sweep = true; } } // Remember if this was a forced sweep bool forced = _force_sweep; // Force stack scanning if there is only 10% free space in the code cache. // We force stack scanning only if the non-profiled code heap gets full, since critical // allocations go to the non-profiled heap and we must be make sure that there is // enough space. double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100; if (free_percent <= StartAggressiveSweepingAt) { do_stack_scanning(); } if (_should_sweep || forced) { init_sweeper_log(); sweep_code_cache(); } // We are done with sweeping the code cache once. _total_nof_code_cache_sweeps++; _last_sweep = _time_counter; // Reset flag; temporarily disables sweeper _should_sweep = false; // If there was enough state change, 'possibly_enable_sweeper()' // sets '_should_sweep' to true possibly_enable_sweeper(); // Reset _bytes_changed only if there was enough state change. _bytes_changed // can further increase by calls to 'report_state_change'. if (_should_sweep) { _bytes_changed = 0; } if (forced) { // Notify requester that forced sweep finished assert(_force_sweep, "Should be a forced sweep"); MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); _force_sweep = false; CodeCache_lock->notify(); } } void NMethodSweeper::sweep_code_cache() { ResourceMark rm; Ticks sweep_start_counter = Ticks::now(); int flushed_count = 0; int zombified_count = 0; int marked_for_reclamation_count = 0; int flushed_c2_count = 0; if (PrintMethodFlushing && Verbose) { tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count()); } int swept_count = 0; assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); assert(!CodeCache_lock->owned_by_self(), "just checking"); int freed_memory = 0; { MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); while (!_current.end()) { swept_count++; // Since we will give up the CodeCache_lock, always skip ahead // to the next nmethod. Other blobs can be deleted by other // threads but nmethods are only reclaimed by the sweeper. nmethod* nm = _current.method(); _current.next(); // Now ready to process nmethod and give up CodeCache_lock { MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); // Save information before potentially flushing the nmethod int size = nm->total_size(); bool is_c2_method = nm->is_compiled_by_c2(); bool is_osr = nm->is_osr_method(); int compile_id = nm->compile_id(); intptr_t address = p2i(nm); const char* state_before = nm->state(); const char* state_after = ""; MethodStateChange type = process_nmethod(nm); switch (type) { case Flushed: state_after = "flushed"; freed_memory += size; ++flushed_count; if (is_c2_method) { ++flushed_c2_count; } break; case MarkedForReclamation: state_after = "marked for reclamation"; ++marked_for_reclamation_count; break; case MadeZombie: state_after = "made zombie"; ++zombified_count; break; case None: break; default: ShouldNotReachHere(); } if (PrintMethodFlushing && Verbose && type != None) { tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after); } } _seen++; handle_safepoint_request(); } } assert(_current.end(), "must have scanned the whole cache"); const Ticks sweep_end_counter = Ticks::now(); const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; { MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag); _total_time_sweeping += sweep_time; _total_time_this_sweep += sweep_time; _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); _total_flushed_size += freed_memory; _total_nof_methods_reclaimed += flushed_count; _total_nof_c2_methods_reclaimed += flushed_c2_count; _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); } EventSweepCodeCache event(UNTIMED); if (event.should_commit()) { event.set_starttime(sweep_start_counter); event.set_endtime(sweep_end_counter); event.set_sweepIndex(_traversals); event.set_sweptCount(swept_count); event.set_flushedCount(flushed_count); event.set_markedCount(marked_for_reclamation_count); event.set_zombifiedCount(zombified_count); event.commit(); } #ifdef ASSERT if(PrintMethodFlushing) { tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value()); } #endif log_sweep("finished"); // Sweeper is the only case where memory is released, check here if it // is time to restart the compiler. Only checking if there is a certain // amount of free memory in the code cache might lead to re-enabling // compilation although no memory has been released. For example, there are // cases when compilation was disabled although there is 4MB (or more) free // memory in the code cache. The reason is code cache fragmentation. Therefore, // it only makes sense to re-enable compilation if we have actually freed memory. // Note that typically several kB are released for sweeping 16MB of the code // cache. As a result, 'freed_memory' > 0 to restart the compiler. if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); log_sweep("restart_compiler"); } } /** * This function updates the sweeper statistics that keep track of nmethods * state changes. If there is 'enough' state change, the sweeper is invoked * as soon as possible. There can be data races on _bytes_changed. The data * races are benign, since it does not matter if we loose a couple of bytes. * In the worst case we call the sweeper a little later. Also, we are guaranteed * to invoke the sweeper if the code cache gets full. */ void NMethodSweeper::report_state_change(nmethod* nm) { _bytes_changed += nm->total_size(); possibly_enable_sweeper(); } /** * Function determines if there was 'enough' state change in the code cache to invoke * the sweeper again. Currently, we determine 'enough' as more than 1% state change in * the code cache since the last sweep. */ void NMethodSweeper::possibly_enable_sweeper() { double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; if (percent_changed > 1.0) { _should_sweep = true; } } class NMethodMarker: public StackObj { private: CodeCacheSweeperThread* _thread; public: NMethodMarker(nmethod* nm) { JavaThread* current = JavaThread::current(); assert (current->is_Code_cache_sweeper_thread(), "Must be"); _thread = (CodeCacheSweeperThread*)current; if (!nm->is_zombie() && !nm->is_unloaded()) { // Only expose live nmethods for scanning _thread->set_scanned_nmethod(nm); } } ~NMethodMarker() { _thread->set_scanned_nmethod(NULL); } }; void NMethodSweeper::release_nmethod(nmethod* nm) { // Make sure the released nmethod is no longer referenced by the sweeper thread CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current(); thread->set_scanned_nmethod(NULL); // Clean up any CompiledICHolders { ResourceMark rm; MutexLocker ml_patch(CompiledIC_lock); RelocIterator iter(nm); while (iter.next()) { if (iter.type() == relocInfo::virtual_call_type) { CompiledIC::cleanup_call_site(iter.virtual_call_reloc()); } } } MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); nm->flush(); } NMethodSweeper::MethodStateChange NMethodSweeper::process_nmethod(nmethod* nm) { assert(nm != NULL, "sanity"); assert(!CodeCache_lock->owned_by_self(), "just checking"); MethodStateChange result = None; // Make sure this nmethod doesn't get unloaded during the scan, // since safepoints may happen during acquired below locks. NMethodMarker nmm(nm); SWEEP(nm); // Skip methods that are currently referenced by the VM if (nm->is_locked_by_vm()) { // But still remember to clean-up inline caches for alive nmethods if (nm->is_alive()) { // Clean inline caches that point to zombie/non-entrant/unloaded nmethods MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } return result; } if (nm->is_zombie()) { // If it is the first time we see nmethod then we mark it. Otherwise, // we reclaim it. When we have seen a zombie method twice, we know that // there are no inline caches that refer to it. if (nm->is_marked_for_reclamation()) { assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); release_nmethod(nm); assert(result == None, "sanity"); result = Flushed; } else { nm->mark_for_reclamation(); // Keep track of code cache state change _bytes_changed += nm->total_size(); SWEEP(nm); assert(result == None, "sanity"); result = MarkedForReclamation; assert(nm->is_marked_for_reclamation(), "nmethod must be marked for reclamation"); } } else if (nm->is_not_entrant()) { // If there are no current activations of this method on the // stack we can safely convert it to a zombie method if (nm->can_convert_to_zombie()) { // Clear ICStubs to prevent back patching stubs of zombie or flushed // nmethods during the next safepoint (see ICStub::finalize). { MutexLocker cl(CompiledIC_lock); nm->clear_ic_stubs(); } // Code cache state change is tracked in make_zombie() nm->make_zombie(); SWEEP(nm); if (nm->is_osr_method()) { // No inline caches will ever point to osr methods, so we can just remove it. // Make sure that we unregistered the nmethod with the heap and flushed all // dependencies before removing the nmethod (done in make_zombie()). assert(nm->is_zombie(), "nmethod must be unregistered"); release_nmethod(nm); assert(result == None, "sanity"); result = Flushed; } else { assert(result == None, "sanity"); result = MadeZombie; assert(nm->is_zombie(), "nmethod must be zombie"); } } else { // Still alive, clean up its inline caches MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } } else if (nm->is_unloaded()) { // Code is unloaded, so there are no activations on the stack. // Convert the nmethod to zombie or flush it directly in the OSR case. { // Clean ICs of unloaded nmethods as well because they may reference other // unloaded nmethods that may be flushed earlier in the sweeper cycle. MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); } if (nm->is_osr_method()) { SWEEP(nm); // No inline caches will ever point to osr methods, so we can just remove it release_nmethod(nm); assert(result == None, "sanity"); result = Flushed; } else { // Code cache state change is tracked in make_zombie() nm->make_zombie(); SWEEP(nm); assert(result == None, "sanity"); result = MadeZombie; } } else { possibly_flush(nm); // Clean inline caches that point to zombie/non-entrant/unloaded nmethods MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } return result; } void NMethodSweeper::possibly_flush(nmethod* nm) { if (UseCodeCacheFlushing) { if (!nm->is_locked_by_vm() && !nm->is_native_method()) { bool make_not_entrant = false; // Do not make native methods not-entrant nm->dec_hotness_counter(); // Get the initial value of the hotness counter. This value depends on the // ReservedCodeCacheSize int reset_val = hotness_counter_reset_val(); int time_since_reset = reset_val - nm->hotness_counter(); int code_blob_type = CodeCache::get_code_blob_type(nm); double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity); // The less free space in the code cache we have - the bigger reverse_free_ratio() is. // I.e., 'threshold' increases with lower available space in the code cache and a higher // NmethodSweepActivity. If the current hotness counter - which decreases from its initial // value until it is reset by stack walking - is smaller than the computed threshold, the // corresponding nmethod is considered for removal. if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) { // A method is marked as not-entrant if the method is // 1) 'old enough': nm->hotness_counter() < threshold // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush) // The second condition is necessary if we are dealing with very small code cache // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. // The second condition ensures that methods are not immediately made not-entrant // after compilation. make_not_entrant = true; } // The stack-scanning low-cost detection may not see the method was used (which can happen for // flat profiles). Check the age counter for possible data. if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) { MethodCounters* mc = nm->method()->get_method_counters(Thread::current()); if (mc != NULL) { // Snapshot the value as it's changed concurrently int age = mc->nmethod_age(); if (MethodCounters::is_nmethod_hot(age)) { // The method has gone through flushing, and it became relatively hot that it deopted // before we could take a look at it. Give it more time to appear in the stack traces, // proportional to the number of deopts. MethodData* md = nm->method()->method_data(); if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) { // It's been long enough, we still haven't seen it on stack. // Try to flush it, but enable counters the next time. mc->reset_nmethod_age(); } else { make_not_entrant = false; } } else if (MethodCounters::is_nmethod_warm(age)) { // Method has counters enabled, and the method was used within // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing // compiled state. mc->reset_nmethod_age(); // delay the next check nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); make_not_entrant = false; } else if (MethodCounters::is_nmethod_age_unset(age)) { // No counters were used before. Set the counters to the detection // limit value. If the method is going to be used again it will be compiled // with counters that we're going to use for analysis the the next time. mc->reset_nmethod_age(); } else { // Method was totally idle for 10 sweeps // The counter already has the initial value, flush it and may be recompile // later with counters } } } if (make_not_entrant) { nm->make_not_entrant(); // Code cache state change is tracked in make_not_entrant() if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold); } } } } } // Print out some state information about the current sweep and the // state of the code cache if it's requested. void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { if (PrintMethodFlushing) { ResourceMark rm; stringStream s; // Dump code cache state into a buffer before locking the tty, // because log_state() will use locks causing lock conflicts. CodeCache::log_state(&s); ttyLocker ttyl; tty->print("### sweeper: %s ", msg); if (format != NULL) { va_list ap; va_start(ap, format); tty->vprint(format, ap); va_end(ap); } tty->print_cr("%s", s.as_string()); } if (LogCompilation && (xtty != NULL)) { ResourceMark rm; stringStream s; // Dump code cache state into a buffer before locking the tty, // because log_state() will use locks causing lock conflicts. CodeCache::log_state(&s); ttyLocker ttyl; xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); if (format != NULL) { va_list ap; va_start(ap, format); xtty->vprint(format, ap); va_end(ap); } xtty->print("%s", s.as_string()); xtty->stamp(); xtty->end_elem(); } } void NMethodSweeper::print() { ttyLocker ttyl; tty->print_cr("Code cache sweeper statistics:"); tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000); tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps); tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed, _total_nof_c2_methods_reclaimed); tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K); }